Weeds are plants that compete with cultivated plants in an agronomic environment and cost farmers billions of dollars annually in crop losses and the expense of efforts to keep weeds under control. Weeds also serve as hosts for crop diseases and insect pests. The losses caused by weeds in agricultural production environments include decreases in crop yield, reduced crop quality, increased irrigation costs, increased harvesting costs, reduced land value, injury to livestock, and crop damage from insects and diseases harbored by the weeds. The principal means by which weeds cause these effects are: 1) competing with crop plants for water, nutrients, sunlight and other essentials for growth and development, 2) production of toxic or irritant chemicals that cause human or animal health problem, 3) production of immense quantities of seed or vegetative reproductive parts or both that contaminate agricultural products and perpetuate the species in agricultural lands, and 4) production on agricultural and nonagricultural lands of vast amounts of vegetation that must be disposed of Herbicide tolerant weeds are a problem with nearly all herbicides in use, there is a need to effectively manage these weeds. There are over 365 weed biotypes currently identified as being herbicide resistant to one or more herbicides by the Herbicide Resistance Action Committee (HRAC), the North American Herbicide Resistance Action Committee (NAHRAC), and the Weed Science Society of America (WSSA).
Plants have chloroplasts in which nuclear encoded proteins are imported. The import function is a key process related to the normal activity of the chloroplast. Genes associated with the chloroplast protein import and processing include but are not limited to the structural genes that encode for translocon at the outer envelope membrane of a chloroplast (Toc), a translocon at the inner envelope membrane of a chloroplast (Tic), a stroma processing peptidase (SPP) and chaperone like proteins associated with the chloroplast protein import system. The import of essential proteins into the chloroplast can be achieved by modulating the level of import proteins produced by the plants nuclear encoded genes. Many enzymes that are targets for herbicide action are nuclear encoded and imported into the chloroplast.
Embodiments of the present invention provide polynucleotide compositions useful for modulating gene expression in a plant, in particular, weedy plants for the purpose of enhancing control of the weeds in an agronomic environment and for the management of herbicide resistant weeds.